B.5.5.6 Deleting Rows from Related Tables

MySQL does not support subqueries prior to version 4.1, or the
use of more than one table in the
DELETE statement prior to
version 4.0. If your version of MySQL does not support
subqueries or multiple-table
DELETE statements, you can use
the following approach to delete rows from two related tables:

If the total length of the
DELETE statement for
related_table is more than 1MB (the default
value of the
max_allowed_packet system
variable), you should split it into smaller parts and execute
multiple DELETE statements. You
probably get the fastest DELETE
by specifying only 100 to 1,000
related_column values per statement if the
related_column is indexed. If the
related_column isn't indexed, the speed is
independent of the number of arguments in the
IN clause.